A horizontal multi-chamber assembled pipe rack mold comprises end molds, an outer mold, a bottom mold, inner molds and inner mold contracting devices. Each end mold comprises two side end mold bodies, a support end mold body, two upper end mold bodies, two cross beams and two rotating shafts; the side end mold bodies and the support end mold bodies are connected through the cross beams, each cross beam is provided with one rotating shaft, the rotating shafts are connected with the upper end mold bodies, and the upper end mold bodies can rotate around the rotating shafts; the bottoms of the upper end mold bodies are provided with fixing bolts matched with the tops of the cross beams; the bottoms of the side end mold bodies and the bottoms of the support end mold bodies are fixed to the bottom mold, the outer mold is arranged on the two axial sides of the end molds, and each inner mold is composed of an upper inner mold plate, trapezoidal rotating shafts and side inner mold plates, wherein the two sides of the upper inner mold plate are connected with the trapezoidal rotating shafts, the bottoms of the trapezoidal rotating shafts are connected with the side inner mold plates, the bottom of the upper inner mold plate is provided with four support rods, and the bottoms of the support rods are connected with the bottom mold; the inner mold contraction devices are arranged in areas formed by the corresponding support rods in an enclosing mode.